RESISTIVITY INVESTIGATION OF SUBSURFACE STRUCTURES ALONG SARKIN PAWA-MANGORO ROAD PAVEMENT, NIGER STATE, NIGERIA
*Jatto S. S., **Sule P. O. and Ahmed A. L.
Department of Physics
Ahmadu Bello University, Zaria, Nigeria
Email: ssjatto@yahoo.com
ABSTRACT
Geophysical investigations involving the Schlumberger vertical electrical sounding (VES) and Wenner horizontal electrical profiling have been carried out along some stable and unstable sections of the Sarkin-Pawa-Mangoro road in Niger State. This is to investigate the geological factors responsible for the incessant pavement failure within the area. The vertical electrical soundings have been carried out along two traverses PA and PB measuring 1350 metres long respectively, one on each side of the road. 28 VES stations at a station separation of 50 metres are on each traverse. The horizontal electrical profiling was carried out with an electrode separation of 10 metres on traverse PA over a distance of 1150 metres. The geoelectric/geologic sections along the stable segments of the road show generally resistive topsoil with resistivity values ranging from 130-600 Ωm. Beneath the unstable segments, the geoelectric sections show low resistivity clay topsoil (20-120 Ωm), water absorbing substratum, and near-surface water table. The electrical profiling indicates conductive zones beneath the unstable sections. The high and low values of the apparent resistivity data of the electrical profiling may be an indication of the natural variation in the composition of the subsurface or the presence of linear features such as fracture, buried ditch/stream channel or shear zones. The unstable sections which correspond to pavement failure can hence be delineated using geophysical investigations and thus enabling necessary remedial actions to be taken when constructing a new road.
Key
words:
Vertical electrical sounding, Mangoro, Geoelectric Section, Resistivity,
Pavement failure, electrical profiling.